Amazon inflating rates after capturing the market, permitting counterfeits, and penalizing sellers offering lower prices off-Amazon, has nothing to do with market efficiency or commoditization.
You've explained what gives Amazon the leverage to set such terms, and why they'd want to set such terms, but you haven't explained why preventing other platforms/sellers from competing on price isn't anti-competitive - you merely asserted that it is so.
It's not anticompetitive because they aren't restricting competition off their platform. They are simply stating that to participate in their marketplace you must adhere to a set of rules.
It is no different than Nike, who requires no discounts on specific products, etc. Amazon isn't prohibiting selling on non-Amazon platforms. Amazon is prohibiting undercutting them if you choose to sell with them.
> It's not anticompetitive because they aren't restricting competition off their platform.
Yes, they are. They are using their influence and market power to prevent others from competing on price, using the threat of economic retribution on their platform. If this isn't anti-competitive, then nothing short of sending assassins on your competitors is.
Nonsense. They are only able to influence your behavior if you use them. It is completely self selected.
It is the exact same thing as is argued by social media companies: they have the right to moderate the content posted on their platforms because it's their platforms. You can do whatever you want on your own site.
> They are only able to influence your behavior if you use them.
Yes, companies cannot influence behavior of people or businesses that have no business relationship with them, direct or indirect. In other words, you are saying that indeed, the only anti-competitive action is sending armed thugs to sabotage your competition. Everything else, every contractual condition, is fair game.
Simultaneously, there must be harsh penalties for abusing that system. See Samsung's use of a patent on display technology to label third party displays as counterfeits, despite not using that patent nor misrepresenting themselves as Samsung screens.
Why shouldn't they be allowed to do this? If you want to sell on their market, you promise not to undercut them.
Amazon exists as a discovery tool for consumers. They don't want third party sellers to get free advertising. That isn't anticompetitive.